In general, a truck where the driver's seating position in the cab is arranged in front of the engine (hereafter called cab-over engine truck) has a pair of cab underframes (or floor underframes) arranged under the cab. This cab underframe includes a front section arranged on the front side, a rising section that rises from the back edge of the front section, and a back section that extends rearward from the upper end of the rising section; wherein a passenger seat is deployed on the back section.    Patent Document 1: JP-A 11-208516